Spark plug



-pl'l 7, 1931. A. R. MosLER 1,799,922

SPARK PLUG Filed May 18, 1928 2j INVENTOR Arkarljlfo/Zef BY 19a DM ATTORNEY Patented Apr, 7, 1931 UNITED *STATES PATENT ol-"FlcE ARTHUR B. MOSLER, 0F NEW YORK, N. Y., ASSIGNOB TO MOSLER IGNITION CORP., OF

' NEW YORK, N. Y., A COBIOATION OF NEW YORK Application led Hay 18, 1928. Serial No. 278,659'.

'In order to secure proper uniformity and certainty of operation in internal combustion engines, it is essential that the spark gap of the spark plug be adjusted within comparatively narrow limits. This may be accomplished in some types of plugs by lforming one or both of the electrodes of a comparatively small diameter wire or rod which permits of bending to obtain proper spacing. For high compression engines such small parts often become heated so as to cause objectionable preignition. For avia.- tion engines, re engines and the like, it. is important that the parts be so accurately and rigidly built that bending of the parts is precluded, retention of adjustment during use is insured, and danger of heating to cause preignition is eliminated, but it is also important that proper, accurate and easy adjustment upon assembly and readjustment after use be permitted.

The present invention relates particularly to the design, construction and operation of electrodes or terminals for forming the spark gap, and the main object is to provide a construction fulfilling the above mentioned desirable conditions.

In order to simplify manufacture of the parts and insure accuracy of assembly and durability in use, it is important that the center electrode be straight and symmetrical and of rigid design. With such central electrode, I provide a second electrode which may be rotatably adjusted about an axis parallel to, but spaced from the central electrode, whereby the spacing of the electrodes may be very accurately set at any desired distance without bending of the parts and without liability of shifting of the parts in use.

I am aware that the provision of a rotatable electrode coaxial with the central electrode has been suggested. This is objectionable as it does not provide for adjustment unless a non-symmetrical central electrode is employed,but that resents diiculties and higher cost in manu acture and accurate assembly. Y

The eccentric positioning of the axis of the outer or side electrode in respect to the central one and the provision of means to facilitate the rotational adjustment, constitute important features of my invention.

In the preferred embodiment of my invention, I provide a simple annular circular disc which may be made by stamping from sheet metal and which has an electrode point adapted to also serve as a 'means for rotating the disc in its eccentrically positioned groove in the base of the plug.

Due to the fact that the disc and the cen tral electrode are not coaxial, the rotation of the disc will bring the electrode point closer to or farther from the central electrode to give the desired spacing.

As one important feature of my invention, I so proportion the parts that when the disc is rotated to one limiting position, the two electrodes will he in contact. By then rotating the disc through apredetermined nuniber of degrees, the exact spacing may be obtained without the need for a gauge or other separate measuring tool. v

As a further feature of my invention I provide a special tool serving both as a means for rotating the disc and for obtaining the desired spacing between the electrodes.

It will be understood that the disc when rotated tothe desired position is securely retained in that position against movement, eX- cept when force is applied by means of some suitable tool.

In the accompanying drawings I have illustrated certain embodiments of my invention, but it will be understood that the invention is not limited to these particular forms and that other forms might be designed within the spirit of my invention without departing from the scope of the appended claims.

In these drawings:

Fig. 1 is 'a central longitudinal section of a spark plug embodying m invention, the lower portion of the plug ing shown in section;

Fig. 2 is an end view of the plug shown 1n F iff. l;

Fig. 3 is a electrode;

Fig. 4 is a perspective view of a tool for adjusting the disc;

Fig. 5 is a central longitudinal section of the tool and terminal portion of the plug in operative engagement;

Fig.' 6 is a section of the terminal portion of a plug showing an alternative construcperspective view of the disc tion;

Fig. 7 is an end view of the parts shown in Fig. 6;

Fig. 8 is a perspective view of the plate from which is formed the rotatable electrode shown in Figs. 6 and 7; y

Fig. 9 is a longitudinal section through the terminal of a plug showing an alternative method of securing the disc in place, and including the tool for accomplishing this;

Fig. 10 is a section similar to a portion of Fig. 9, but showing the retaining flange in final position; and

Fig. 11 is an end view similar to a portion of Fig. 27 but showing graduation marks to facilitate adjustment. p

In Fig. 1 l have shown my invention as applied to a type of plug, all. of the features of which, except the electrodes may be constructed as shown in my prior Patent 1,588,489, issued Jan. 15, 192e.

rlhis plug has a main body portion or shell 10 exteriorly threaded to adapt it for mounting in the proper position in respect to the combustion chamber. Projecting through the center of the plug is a bar or rod l1 carried by, but insulated from a gland 12 which ,may be threaded into the shell and seated on a gasket 13. The outer end of this rod has suitable means 14e for the attachment of an electrical conductor thereto, while the inner end has an approximately hemispherical head 15 of larger diameter than the body of the rod and disposed in the inner end of the shell or body 10. rlhe inner surface of the peripheral wall of the latter curves inwardly to provide an annular air space 16. The center electrode is in the form of a short rod 17 which may be of nickel or other suitable non-corrosive metal.

The details of construction of the parts so far described are not essential to the carrying out of the invention and may be varied within wide limits.

ln carrying out my invention the end of the body or shell l0 is provided with an annular groove 18 which is of circular form, but slightly eccentric in respect to the axis of the straight symmetrical central electrode 17. `Within this groove there is mounted an annular disc 19 which has a central opening into or toward which the central electrode 17 extends.

It also preferably has-an electrode point 2O formed integral and projecting in radially from the annular wall.

This disc is mounted in the groove 18 in such manner that it is normally rigidly secured, but may be rotated about its axis to vary the spaclng of the electrode point 20 from the central electrode 17.

As illustrated the disc has a bevelled edge and after the disc is placed in the groove, a portion of the metal at the outer edge of the groove is swaged or otherwise forced inwardly to engage the bevelled edge of the disc and hold Athe disc in position. When the disc has been rotated to give the desired adjustment, a sharp'pointed tool may-be drlven into the retaining iange or the contacting surfaces of the disc and flange to slightly deform the metal and lock the parts against unintentioned relative rotation.

Obviously the disc may be retained in position in other ways. For instance, in Figs. 9 and 10 l have shown a disc 19a which has a cylindrical rather than a bevelled edge, and the end of the shell or body 10al has a iange 21 which may be forced inwardly by a suitable tool 22 to engage the outer surface of the disc as shown in Fig. 10. After this Harige has been forced inwardly and the disc has been rotated to the proper adjustment, the parts may be locked by the use of a pointed tool as above described. Other means might be employed for retaining the disc in position.

For use in adjusting the disc above described and for gauging the distance between the electrodes, I preferably employ 'such a tool as that shown in Figs. 4 and 5.

rlhis includes a shank or body portion 2d of approximately the diameter of the opening in the disc and with a recess 25 in the end to receive the center electrode and a slot 26 to receive the electrode point 20. The shank is provided with a groove 27 extending lengthwise thereof and in this groove is disposed a metal strip 28 constituting a gauge and of a thickness equal to the desired spacing between the electrodes. The shank at its outer end is provided with a handle 29 and the gauge strip 28 has an elongated loop 30 encircling the portion of the handle projecting across a slot 3l in the outer end of the shank. This permits of a limited longitudinal movement of the gauge and by reason of the flexibility of the metal forming the loop, permits the removal of the gauge and the substitution of another of ditferent thickness if desired.

ln using the tool the shank is inserted through the opening in the disc with the electrode point 20 projecting into the slot 26. lf there is sucient spacing between the 1 center electrode 17 and the side electrode 20 the gauge may extend between the two electrodes as shown in Fig. 5. If there is not sufficient spacing the gauge may rest on the outer surface of the disc due to the fact that the gauge can move endwise of the tool through a distance determined by the loop 30.

Upon rotating the tool the disc will be forced to rotate and such movement is continued until the gauge may enter between the electrodes. The rotation is continued or reversed until the gauge is pinched between the two electrodes. Thereafter the tool is turned in the reverse direction through a. very slight angle sufficient to release the gauge and leave the two electrodes spaced apart to a distance equal to the thickness of the gauge. The disc is then locked in position as above described.

Preferably the handle 29 is provided with a sharp point 32 at one end, whereby upon placing in proper position and striking the opposite end a blow with a hammer or 'other implement'. the metal is deformed to prevent rotation of the disc. This deformation is not to such an extent as will preclude the later rotation and readjustment of the disc by inserting the tool and applying a sufficient rotation force thereto.

rllhe tool may thus be used not only in the original assembly of the parts, but in readjustment after.

lt is not essential that the tool be provided with the gauge strip 23. If this is omitted the annular surface of the disc may be provided with graduation marks 33 as shown in Fig. ll and the adjacent edge of the body of the plug may be provided with an indicating mark 34.

The disc may be rotated until the two electrodes are in contact and the particular one of the graduation marks 33 which is in registry with the mark 34 may be noted. The disc may then be rotated in the opposite direction through a predetermined arc, as indicated by the graduation marks. Thus the desired spacing may be accurately obtained without the use of a gauge between the two electrodes.

Obviously the marks33 and 34 may be reversed, that is the graduation marks on the body of the plug and the mark 34 on the disc.

Numbers may be used adjacent to the several graduation marks if desired to indicate the number of degrees, but ordinarily this is not essential if the graduation marks be spaced a predetermined number of degrees apart and the angular distance for obtaining a specified spacing has been determined.

Although the rotatable element is preferably in the form of a disc, it may be in the form of a sheet metal strip, such as shown in Figs. 6, 7 and 8. In these figures I have shown a strip of sheet metal 35 which may be fiattened intermediate of its ends so as to increase the width and reduce the thickness,

edge for juxtaposition to the central electrode.

vided with beads, ridges or lianges 37 and the inner surface of the spark plug shell or body A10b may have an annular groove 38 upon its inner surface, this groove being eccentrically ppsitioned in respect to the center electrode 1 b'.

The strip as shown in Fig. 8 may be bent to substantially U-shape with the flanges or ridges 37 upon the outer side vof the arms of the U and inserted into the end of the plug until these flanges 37 Venter the groove 38. The surface of the strip adjacent to the anges may be provided with roughened portions 39 w ich by engagement with the wall of the shell will normally prevent rotation. The strip has sufficient resiliency so that after being inserted it presses' outwardly against the surrounding walland remains in fixed position. v

The center electrode 17 Z1 projectsinto the aperture 36 of this U-shaped rotatable electrode and due to the eccentricity of the groove 38 the point of the center electrode will be eccentric in respect to the opening 36.

rlhus by rotating the outer electrode the distance between the center electrode and the nearest edge of the opening 36 may bevaried to provide the desired spacing for the spark Fis the electrode projects beyond the end of the body of the plug it may be rotated by means of an ordinary wrench or other tool, the body of the plug being held in a vise.

This type of construction is particularly applicable to various forms of plugs such as are now on the market and in which the center electrode is supported in a porcelain or other insulator 40.

The center electrode may be of any suitable metal, but preferably the terminal portion may be made of platinum or other material best adapted to withstand the action of the electric spark. Y

The rotatable electrode may be made of the same material as the disc shown in Fig. 3, that is nickel or other such non-corrosive metal.

Having thus described my invention what l claim as new and desire to secure by Letters Patent is:

l. A spark plug including a central electrode, and an annular electrode encircling the central electrode and mounted for rotation about an axis eccentrically disposed in respect to the central electrode.

2. A spark plug having a central electrede, andan annular electrode having its axis eccentrically disposed in respect to the end portions of the strip may be prothe spark gap 'spacing between said electrodes.

4. A spark plug having a shell provided adjacent to its inner end with an eccentrically disposed groove, an axial symmetrical electrode supported by and insulated from said shell, and a second electrode mounted in said groove and rotatable in respect to the first mentioned electrode to vary the spark gap l spacing.

5. A spark plug having a body portion, an axial symmetrical centrally disposed electrode carried by and insulated from said body portion, and a second electrode carried by said body portion and rotatable about an axis eccentrically positioned in respect to the first mentioned elect-rode.

6. A spark plug having a shell, a centrally disposed axial symmetrical electrode carried by and insulated from said shell, and an annular electrode carried by said shell and having an inwardly projecting electrode point, said second electrode being rotatable about an axis eccentrically disposed in respect to the iirst electrode to vary the spacing of said first electrode and said electrode point.

A spark plug having an axial symmetrical centrally disposed electrode, and an annular disc encircling the first electrode and rotatable about an ams eccentrically disposed in res ect to the latter.

8. l spark plu having a shell, a centrally disposed electroe insulated therefrom, an annular electrode carried by said shell, encircling said iirst electrode, and rotatable about an axis eccentric to the axis of the latter, the eccentricity oi the second electrode and the relative position oi*l the parts being such that upon rotation of said electrode, the two electrodesmaybe brought into or out of Contact.

9. A sparh plug having a shell, a centrally disposed electrode insulated therefrom, an annular electrode carried by said shell, encircling said first electrode, and rotatable about an axis eccentric to the axis of the latter,- the eccentricity of the second electrode and the relative position ot the parts being such that upon rotation ot said electrode, the two electrodes may be brought into or out of contact, said shell and second electrode having cooperating graduation marks, whereby a predetermined spacing ot the electrodes may be obtained by rotation of the second electrode through a predetermined angle.

l0. A spark plug having a shell provided 

